Conventionally, an excimer lamp is used as a light source of ultraviolet rays for photochemical reaction. For example, such an excimer lamp is disclosed in Japanese Patent No. 3178162.
FIGS. 11, 12A and 12B are diagrams for explaining the conventional excimer lamp 1 disclosed in Japanese Patent No. 3178162. FIG. 11 is a perspective view of the excimer lamp 1. FIG. 12A is a cross sectional view of an arc tube 21 of the excimer lamp 1 shown in FIG. 11, taken along a direction of a tube axis thereof. FIG. 12B is a cross sectional view thereof, taken along a direction perpendicular to the tube axis of the arc tube 21 shown in FIG. 12A (a cross sectional view thereof taken along a line F-F of FIG. 12A). In FIGS. 12A and 12B, the same reference numerals as those of FIG. 11 are assigned to the same structural parts as those shown in FIG. 11.
Lid portion members 221 and 222 are arranged so as to cover both ends of the straight tube shaped arc tube 21 of the excimer lamp 1, which are free ends. Sealing members 231 and 232 are filled up between the arc tube 21 and the respective lid portion members 221 and 222, so that the arc tube 21 and the respective lid portion members 221 and 222 are connected to each other. Thereby, an electric discharge container 2 which is made up of the arc tube 21, the lid portion members 221 and 222, and the sealing members 231 and 232 is formed.
A gas pipe 2221 is provided in the second lid portion member 222. After air in an inner space 24 of the electric discharge container 2 is discharged from the gas pipe 2221, krypton (Kr) and fluorine (F2) gas is enclosed as light emitting gas. A sealing portion 2222 is formed by welding the gas pipe 2221 with pressure after the enclosure of the light emitting gas.
A pair of external electrodes 31 and 32 which are electrically separated from each other is provided on the outer surface of the arc tube 21. Leads 41 and 42 are electrically connected to the respective end portions of the external electrodes 31 and 32 in the longitudinal direction thereof by, for example, solders 51 and 52.
The leads 41 and 42 are connected to a power supply (not shown). Electric discharge occurs in the arc tube 21, between the pair of external electrodes 31 and 32 to which electric power is supplied from the leads 41 and 42, when a lamp 1 is lit. The light emitting gas enclosed in the inner space 24 of the electric discharge container 2 is ionized, so that, for example, krypton ions and fluorine ions are formed in the inner space 24 of the electric discharge container 2, whereby excimer molecules which consist of krypton-fluorine are formed, and, for example, light with a wavelength of approximately 248 nm is generated.